
Two-sample t test with equal variances
------------------------------------------------------------------------------
   Group |     Obs        Mean    Std. Err.   Std. Dev.   [95% Conf. Interval]
---------+--------------------------------------------------------------------
 control |  17,281     21848.5    173.4844    22805.77    21508.46    22188.55
experime |  17,281    21799.74    172.7707    22711.96    21461.09    22138.39
---------+--------------------------------------------------------------------
combined |  34,562    21824.12    122.4182     22758.6    21584.18    22064.06
---------+--------------------------------------------------------------------
    diff |            48.76204    244.8399               -431.1321    528.6562
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    diff = mean(control) - mean(experime)                         t =   0.1992
Ho: diff = 0                                     degrees of freedom =    34560

    Ha: diff < 0                 Ha: diff != 0                 Ha: diff > 0
 Pr(T < t) = 0.5789         Pr(|T| > |t|) = 0.8421          Pr(T > t) = 0.4211
